A well known type of structure for a vehicle air bag module comprises an inflator and an air bag disposed within a container. The container is generally formed by a reaction device (e.g., a reaction can or reaction plate) and a cover coupled to the reaction device to complete an enclosure for the inflator and the air bag. The module is assembled by fastening the inflator and air bag to the reaction device, and then fastening the cover to the reaction device. The module is generally installed in a vehicle by coupling a part of the container (usually the reaction device) to a structural part of the vehicle. At the onset of a collision, the inflator produces an inert gas (e.g., nitrogen) which is directed under pressure against the air bag to force the air bag out of the container and into the passenger compartment.
One known type of inflator for a vehicle air bag module is shown in Wipasuramonton, U.S. Pat. No. 4,938,501. The inflator comprises a substantially cylindrical housing which encloses solid gas generating material. Gas dispensing nozzles are formed in the cylindrical housing and are disposed along a substantial portion of the length of the housing. The cylindrical housing is impact extruded and has a threaded boss extruded in one piece with and extending outwardly from an end wall of the housing. The boss has an asymmetrical design that enables the inflator to be located and aligned within the air bag module.
Other known types of cylindrical inflators for air bag modules are shown in Hamilton, et al, U.S. Pat. No. 4,200,615; Wilhelm, U.S. Pat. No. 4,158,696; Schneider, U.S. Pat. No. 4,890,860; and Risko, U.S. Pat. No. 4,153,273. In each of the foregoing patents, the cylindrical inflator is specifically designed to be side-loaded into a reaction can or other container for an air bag module using a threaded stud extending through an aperture in the container. Moreover, in each of these patents, the cylindrical inflator includes a separate alignment device, such as an alignment pin or key attached to the housing of the inflator, which properly aligns the cylindrical inflator in the module. With such structure, even after the threaded stud is inserted into the module aperture, the pin or key on the inflator housing must be properly aligned with a groove or notch in the module to orient the inflator properly with respect to the module. Thus, in order to automate the process of assembling a cylindrical inflator into a module, it would be necessary to automate the process of inserting the cylindrical inflator into the reaction can or other container for the module and orienting the inflator in the module to align the pin or key on the inflator housing with the groove or notch on the module.
Another known type of inflator for a vehicle air bag module is shown in Bachelder, U.S. Pat. No. 4,915,410. The inflator comprises an outer cylindrical housing adapted to be located in a cradle formed in a wall of the air bag container and maintained in the cradle by a spring clip which is attached to the container. An alignment pin on the inflator housing is designed to be received in a cooperating aperture in the cradle to orient the inflator properly in the cradle. However, in order to automate assembly of the Bachelder inflator into the module, it would be necessary to automate the process of: (i) orienting the inflator so that the alignment pin on the inflator will mate with the cooperating aperture in the cradle as the inflator is being inserted into the cradle, and (ii) thereafter securing the clip to the container to retain the inflator in the cradle.
Yet another more recent type of cylindrical inflator is shown in co-pending application Ser. No. 07/493,962 entitled, "Air Bag Module Construction and Assembly Technique", assigned to the assignee of the present invention. In a preferred embodiment of that application, a cylindrical inflator housing has flanges extending along the length of the housing. The inflator housing is formed by impact extrusion techniques, and the flanges are extruded in one piece with the inflator housing and form a reaction device integral with the inflator housing. The flanges have apertures which enable the inflator to be bolted or riveted to a structural part of the vehicle.
The design of the inflator of Ser. No. 07/493,962 is believed to be useful in facilitating the assembly of a cylindrical inflator with an air bag module. Specifically, the flanges on the inflator can be fastened to an air bag/cover subassembly to incorporate the inflator and reaction device into an air bag module. However, applicants believe that for longer cylindrical inflators, it may be difficult to extrude the flange in one piece with the inflator housing with enough dimensional precision to avoid significant finishing steps. Moreover, impact extruding a flange in one piece with an inflator housing means that in order to form inflator housings of differing lengths, the inflator housings may need to be struck from different extrusion dies. Still further, when the inflator is formed in one piece with a flange, it is still necessary to properly align the inflator in the module in order to automate assembly of the module.